Objects to be weighed, such as confectionary or the like, which are weighed by a combination weigher to have a predetermined weight, are generally packaged by a packaging machine. A schematic construction of such a system that weighs and packages objects to be weighed is shown in FIG. 1.
The system shown in FIG. 1 includes a packaging machine 21 disposed below a combination weigher. The combination weigher, whose operation is entirely controlled by a control unit 10, includes a plurality of weighing hoppers 1 arranged in a circle shape, a collecting chute 3 provided below the plurality of weighing hoppers 1, and a collecting hopper 4 provided at an outlet of the collecting chute 3. To each weighing hopper 1, a feeding hopper (not shown) or the like disposed thereabove feeds objects to be weighed. Furthermore, each weighing hopper 1 is attached with a weight sensor (not shown), such as a load cell, which measures the weight of the objects to be weighed inside the weighing hopper 1 and sends the measured value to the control unit 10. The control unit 10 performs combination calculation based on the measured values of the plurality of the weighing hoppers 1, determines a combination of hoppers that will discharge the objects to be weighed, from among the plurality of weighing hoppers 1, and opens and closes gates 2 of the weighing hoppers 1 forming the combination, so that the objects to be weighed are discharged from the weighing hoppers 1. The objects to be weighed discharged from the weighing hoppers 1 slide down on the collecting chute 3, pass through the outlet provided at the lower part of the collecting chute 3 to be temporarily accumulated in the collecting hopper 4, and then are sent out to the packaging machine 21 when a gate 5 of the collecting hopper 4 is opened and closed under the control of the control unit 10.
The packaging machine 21, while manufacturing bags, fills the objects to be weighed discharged from the combination weigher in these bags for packaging. In this packaging machine 21, a sheet of a wrapping material 27 withdrawn from a roll 26 of the wrapping material is caused to be wound around a forming tube 23 to form a cylindrical shape, is suctioned by a pulldown belt (not shown) to be transferred downward, and the superposed vertical edges of the cylindrically formed wrapping material are sealed (sealing by fusion adhesion) by a vertical sealing machine 24. Then, the objects to be weighed which have been weighed by the combination weigher fall into a funnel 22 of the packaging machine, pass through the forming tube 23, and are filled into a preceding bag 28. A horizontal sealing machine 25 disposed under the forming tube 23 performs a horizontal sealing (sealing by fusion adhesion) across the upper end of the preceding bag 28 and the lower end of the following bag. This horizontal sealing forms the preceding bag 28 into a complete bag with its upper and lower ends sealed, because the lower end has been sealed by the previous horizontal sealing. The horizontally sealed portion is then cut at the center by a cutter built in the horizontal sealing machine 25 so that the preceding bag and the following bag are separated from each other.
With regard to the above construction, a timing chart is shown in FIG. 5, which illustrates the operation of the combination weigher and the packaging machine in the case where the combination weigher is not provided with the collecting hopper 4. In FIG. 5, T1 indicates a discharge cycle time of the combination weigher, and T2 indicates a packaging cycle time that consists of a stopping time Tc and an operating time (sealing time) Td of the horizontal sealing machine 25 of the packaging machine 21. Since the combination weigher and the packaging machine operate in association with each other, T1 and T2 become an equal time. Also, Ta indicates a gate open time of the weighing hopper 1, and Tb indicates a bag accommodating time required to accommodate from tip to tail of a bath of the objects to be weighed discharged from the combination weigher into the bag 28 in the packaging machine 21.
In this case, because of the absence of the collecting hopper 4, the objects to be weighed discharged from the weighing hoppers 1 slide down on the collecting chute 3 and fall directly from the outlet of the collecting chute 3 into the funnel 22 of the packaging machine 21. At this time, due to the fact that the objects to be weighed bounce back and thereby move in unwanted directions on the collecting chute 3, or due to the unevenness in friction of objects to be weighed with the collecting chute 3, there are variations in arrival time of the objects to be weighed at the outlet of the collecting chute 3, thereby increasing the length of from tip to tail of the batch of the objects to be weighed discharged from the outlet of the collecting chute 3, and thus increasing the time taken from the fall of the objects to be weighed until they are completely accommodated into the bag 28. As shown in FIG. 5, the gate 2 of the weighing hopper 1 is opened during the time Ta, and all of the objects to be weighed are discharged from the weighing hopper 1 within this time Ta. On the other hand, the bag accommodating time Tb required to accommodate from the tip to tail of the batch of the objects to be weighed into the bag 28 of the packaging machine 21 is longer than the gate open time Ta of the weighing hopper 1. With the speed up of packaging machines in recent years, if the stopping time Tc of the horizontal sealing machine 25 is shortened, and the bag accommodating time Tb becomes longer than the stopping time Tc of the horizontal sealing machine 25 as shown in FIG. 5, the objects to be weighed arrive during the operation of the horizontal sealing machine 25, so that the objects to be weighed get stuck at the horizontal sealing machine 25. This causes not only the production of defective packages, but also damages to the horizontal sealing machine 25.
For the above stated reason, the collecting hopper 4 is conventionally provided so as to temporarily accumulate the objects to be weighed discharged from the weighing hoppers 1 in the collecting hopper 4 before being discharged into the packaging machine 21. FIG. 6 shows the timing chart, illustrating the operation of the combination weigher and the packaging machine in that case. In FIG. 6, Te indicates a gate open time of the collecting hopper 4, Tf indicates a gate close time, and Tg indicates time required to accommodate all of the objects to be weighed discharged from the weighing hoppers 1 into the collecting hopper 4.
In this case, since all of the objects to be weighed discharged from the weighing hoppers 1 are temporarily accumulated in the collecting hopper 4, and then discharged into the packaging machine 21, the bag accommodating time Tb of the objects to be weighed in the packaging machine 21 is reduced, so that the objects to be weighed are entirely accommodated in the bag within the stopping time Tc of the horizontal sealing machine 25.